Chicago, Illinois Revisions
MILEPOST 1559
Chicago's forecast for Friday has moved 8°F colder
60°F in the 20261030T18:00Z run, 52°F in the 20261101T12:00Z — the 2nd-largest revision of the 7 cities on the roster that moved at all. The current run's 10th-to-90th percentile spread at that hour is 8°F.
Successive cycles do not merely refresh a forecast; they leave a trail. For Friday, November 6 at 21Z in Chicago, that trail runs from 59.7°F in the 20261030T18:00Z cycle to 51.6°F in the 20261101T12:00Z — a move of -8.1°F across 8 runs.
The change is about half the run's 10th-to-90th percentile spread, so the earlier forecast is still inside the current range of outcomes.
Model NBM-QMD, via api.weather.city /v1/history. Percentiles are the same run's own.
The numbers in this piece, with what they are measured against
| forecast revision for Friday at 21Z api.weather.city /v1/history (nbm-qmd) |
-8.1 °F | normal 0.0 °F · 2 of 7 8 synoptic cycles |
| 10th-to-90th percentile spread at that hour api.weather.city (nbm-qmd) |
8.3 °F | normal 8.1 °F current run |
- Milepost
- 1559 · laid 2026-11-01T22:25:23Z
- Model
- nbm-qmd · cycle 20261101T12:00Z
- Desk
- revision v1
- Method
- the same valid time read from successive synoptic cycles; the move is last run minus first run
- Source
- https://api.weather.city/v1/history
- Digest
- b4dfe53bec3431595af9faaafb9ff0327ef7b88dd90664e4807d75d1b07463ac
- Machine
- JSON